UNIT 6 – HUMAN PHYSIOLOGY

List the source, substrate and product of lipase.

Lipase is an enzyme that hydrolyzes fats to fatty acids and glycerol. \n \n Source: pancreas (secreted into small intestine) \n Substrate: triglyceride \n Product: glycerol and three fatty acids \n Optimal pH: 7-8

Outline the structure and function of enzymes immobilized in the cell membrane of small intestine epithelial cells. 

The final step in digestion of dietary carbohydrates and proteins occurs on the face of small intestinal epithelial cells, in the immediate vicinity of the protein transporters which will move the resulting sugars and amino acids into the cells. The enzymes responsible for this final stage of digestion are not free in the intestinal lumen, but rather, tethered as integral membrane proteins in the cell membrane of the epithelial cells.

Outline the digestion and absorption of lipids in humans.

Fats (triglycerides) are digested into fatty acids and glycerol. Pancreatic lipase breaks down triglycerides into free fatty acids and monoglycerides. Pancreatic lipase works with the help of the salts from bile secreted by the liver and the gallbladder. \n Bile salts attach to triglycerides and help to emulsify them; this aids access by pancreatic lipase because the lipase is water-soluble, but the fatty triglycerides are hydrophobic and tend to orient toward each other and away from the watery intestinal surroundings. The bile salts act to hold the triglycerides in their watery surroundings until the lipase can digest them into the smaller fatty acid components that are able to enter the villi for absorption via diffusion.

**Explain how the structure of the villus is adapted for absorption.**

Villi are finger-like projections of the small intestine mucosa that increase the surface area for better absorption of the products of digestion. 

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Microvilli on the villi epithelial cells further increase surface area to improve absorption. 

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The epithelium is a single layer thick, which allows fast diffusion of nutrients from the small intestine lumen into the blood. 

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Capillary bed within the villi maintain a concentration gradient of nutrients (by constantly carrying away absorbed nutrients) so that the rate of diffusion is higher. 

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Lacteal in villus to absorb fatty acids and carry them away from small intestine.

Draw the villi as viewed in cross section.

Capillary \n Epithelial cell \n Lacteal \n Goblet cell

State the function of the villus goblet cell.

Goblet cells are found scattered among the epithelial lining of the small intestine. These cells secrete mucus. Mucus is a slippery aqueous secretion that protects the epithelial cells and serves as a lubricant for the digested food material as it passes through the digestive system.

Describe the absorption of fats by villus epithelial cells.

Fat molecules (triglycerides) are digested by pancreatic lipase within the lumen of small intestine. The products of the digestion are fatty acids, monoglycerides and glycerol, which are absorbed into the epithelial cells on villi.

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The fatty acid **diffuse** across the epithelial cell membrane. Within the epithelial cell, they are again converted into triglycerides. The triglycerides are coated with proteins to form chylomicrons (a lipoprotein) which then enter into lacteals by exocytosis.

Describe absorption of glucose by villus epithelial cells.

Carbohydrate molecules such as starch are digested by pancreatic enzymes (eg amylase) within the lumen of small intestine. Additional digestion of carbohydrates may occur through enzymes embedded within the villi epithelial cells. The products of the digestion are monosaccharides which are absorbed into the epithelial cells on villi.

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Glucose cannot pass through the plasma membrane by simple diffusion because it is polar and therefore hydrophilic. Glucose is transported into the epithelial cell coupled to the movement of sodium ions into the cell through a sodium-glucose cotransport protein. The cotransport protein couples transport of sodium down its concentration gradient (established by the **active transport** of sodium out of the cell by the sodium-potassium pump) into the cell with the transport of glucose **against its concentration gradient** into the cell. Active transport requires ATP (from many mitochondria within the cells). 

Describe transport of glucose into and through villi capillaries.

Glucose is transported *in to* the epithelial cell from the small intestine lumen through a **sodium-glucose cotransport protein.** 

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Then, the glucose moves *out of* the epithelial cell and moves into the villi capillary. **Glucose channels** allow the glucose to move by **facilitated diffusion** into blood capillaries in the villus.

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Glucose in the blood is then carried via the hepatic portal vein to the liver where excess glucose can be absorbed by liver cells and converted to glycogen for storage.

Outline the function of the liver in digestion.

production of bile

Outline the function of the gallbladder in digestion.

The gallbladder **stores bile** produced in the liver until it is needed for digesting fat in the small intestine. Bile travels through the bile ducts and is released into the small intestine where it emulsifies large masses of fat. The emulsification of **fats** by bile turns the large clumps of fat into smaller pieces that have more surface area and are therefore easier for lipase to digest.

Outline the function of the large intestine in digestion.

absorbs water and vitamins

Outline the function of the submucosa layer of tissue found in the wall of the small intestine.

submucosa is located under the mucosa

provides blood vessels, lymphatic vessels, and nerves

Outline the function of the serosa layers of tissue found in the wall of the small intestine.

The **serosa** forms the outermost layer of small intestines and functions as connective tissue. It helps suspend the gut in abdominal cavity by attaching itself to surrounding structures.

Outline the role of elastic and muscle tissue in arteries.

The tunica media is the middle layer of an artery wall. It is a thick layer containing smooth muscle, elastic fibers and collagen that encircle the vessel. The muscle and elastic fibers assist in maintaining blood pressure between pump cycles. \n \n To cope with blood pressure, the muscles and elastin in the artery walls hold them in shape and allow them to to stretch in response to each pulse. This elasticity also helps to maintain a relatively constant pressure in the arteries despite the pulsating nature of the blood flow.

Describe the structure and function of the three layers of artery wall tissue.

**Tunica externa**- A tough outer layer of connective tissue the adheres the vessel to the surrounding tissue.

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**Tunica media**- A thick layer containing smooth muscle, elastic fibers and collagen that hold arteries in shape and allow them to to stretch in response to each pulse.

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**Tunica intima**- A smooth endothelium forming the lining of the artery. Allows blood to flow through the vessel with minimal resistance. 

Describe the mechanism used to maintain blood flow in arteries between heartbeats.

During systole, when new blood is entering the arteries, the artery walls stretch to accommodate the increase of pressure of the extra blood. During diastole, the walls return to normal because of their elastic properties. The **elastic recoil of the arteries** allows the artery to exert an inward force to maintain blood pressure. As the muscles and elastic fibers recoil, they further propel the blood, maintaining blood flow in the arteries between heartbeats. 

Outline the cause and effect of vasoconstriction.

Vasoconstriction is the narrowing of blood vessels resulting from contraction of the muscles in the tunica media layer of the vessel wall. When blood vessels constrict, blood flow to a region is decreased. \n \n Vasoconstriction in arteries near the skin surface can occur when the body is exposed to cold. This makes less blood reach the surface, reducing the radiation of heat from the body.

Outline the cause and effect of vasodilation.

Vasodilation is the widening of blood vessels resulting from relaxation of the muscles in the tunica media layer of the vessel wall. When blood vessels dilate, blood flow to a region is increased. \n \n Vasodilation in arteries near the skin surface can occur when the body is exposed to heat. This makes more blood reach the surface, increasing the radiation of heat from the body. \n \n When exercising, vessels will dilate bringing more oxygen to the metabolically active cells. if there is a localized infection or cut, vessels will dilate, bringing more immune cells and/or clotting factors to to affected tissue. \n \n Pharmaceutical vasodilators are used in medicine to decrease blood pressure.

Describe the structure and function of capillaries.

Capillaries are the smallest blood vessels in the body, connecting the arterioles to venules. Capillaries are composed of only two layers of cells; an endothelial layer surrounded by a basement membrane. The capillary lumen is so narrow that red blood cells need to flow through them single file. Capillaries are highly branched to increase the exchange surface area and minimize the diffusion distance.

\n Exchange of gases and other substances occurs in the capillaries between the blood and the surrounding cells and their tissue fluid (interstitial fluid). For capillaries to function, their walls must be "leaky", allowing substances to pass through. There are three major types of capillaries, which differ according to their degree of “leakiness:” continuous, fenestrated, and sinusoid capillaries.

Outline the roles of gravity and skeletal muscle pressure in maintaining flow of blood through a vein.

If blood is to flow from the veins back into the heart, the pressure in the veins must be greater than the pressure in the atria of the heart. Luckily, the pressure in the atria during diastole is very low. \n \n The pressure within the veins can be increased by the contraction of the surrounding skeletal muscle. This mechanism, known as the skeletal muscle pump, helps the lower-pressure veins counteract the force of gravity, increasing pressure to move blood back to the heart. As leg muscles contract, they exert pressure on nearby veins with their numerous one-way valves. This increased pressure causes blood to flow upward, back to the heart against the force of gravity.

Outline the structure and function of a pocket valve.

Blood pressure in veins is much lower than that in the arteries. Veins must prevent it from flowing in the wrong direction. Valves in the veins function to keep blood moving in one direction. Theses valves are bicuspid (two) flap like structures made of elastic tissue and are often called "pocket valves" in reference to their shape.

Compare the circulation of blood in fish to that of mammals.

In fish, there is single pump circulation. The heart only has one atrium and one ventricle. The oxygen-depleted blood that returns from the body enters the atrium, and then the ventricle, and is then pumped out to the gills where the blood is oxygenated, and then it continues through the rest of the body. \n \n In mammals there is double pump circulation. The heart has two atria and two ventricles. The right side of the heart receives blood returning back from the body; this “deoxygenated” blood enters the right atrium and then the right ventricle to be pumped to the lungs were the blood will be oxygenated. The oxygenated blood from the lungs enters the left ventricle via the left atrium and is then pumped out into the larger body circulation.

Explain why the mammalian heart must function as a double pump.

**There must be a double pump in order to create enough pressure to move the blood throughout the entire body.** Pressure is needed to move blood through the resistance of a large network of blood vessels like arteries, capillaries, and veins. 

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A single pump (a) would require such a force that the lungs capillaries would be damaged by the high pressure blood moving through or (b) wouldn't supply enough force to move blood through the lung capillaries for oxygenation and then continue on to the tissue capillaries. 

Outline the role of cells in the sinoatrial node.

The sinoatrial node (SA node) is a group of cells located in the wall of the right atrium of the heart that have the ability to spontaneously and regularly produce an electrical impulse (action potential) that travels through the heart causing it to contract. The SA node is known as the heart's "pacemaker."

Describe the propagation of the electrical signal from the sinoatrial node through the atria and ventricles.

The cardiac conduction system is a group of specialized cardiac muscle cells in the walls of the heart that send signals to the heart muscle causing it to contract. The sinoatrial node (SA node, "pacemaker") starts the sequence by causing the atria to contract. From the SA node, the signal travels to the atrioventricular node (AV node), through the bundle of His, down the bundle branches, and through the Purkinje fibers, causing the ventricles to contract.

Outline the action of nervous tissue that can regulate heart rate.

Heart rate is intrinsically determined by the pacemaker activity of the sinoatrial node (SA node) located in the wall of the right atrium. However, the pace of the SA node can be changed by impulses (action potentials) brought to the heart through nerves from the medulla of the brain. Neural input can influence heart rate, cardiac output, and contraction forces of the heart. \n \n The vagus nerves (parasympathetic) can reduce the heart rate and the force of contraction of the heart. \n \n Cardiac sympathetic nerves (sympathetic) can increase the heart rate and the force of contraction of the heart.

List factors that will increase heart rate.

* Epinephrine hormone
* Increased thyroid hormones
* Levels of various ions
* Increased body temperature
* Altitude
* Exercise
* Caffeine
* Nicotine

List factors that will decrease heart rate.

* Acetylcholine neurotransmitter
* Decreased thyroid hormones
* Levels of various ions
* Decreased body temperature
* Anticipation of relaxation
* Reduced oxygen availability in cardiac cells

Outline William Harvey’s role in discovery of blood circulation.

William Harvey (1578-1657), observing the heart in living animals, he was able to show that the valves in the veins permit the blood to flow only in the direction of the heart and to prove that the blood circulated around the body and returned to the heart. In his words:

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*"It has been shown by reason and experiment that blood by the beat of the ventricles flows through the lungs and heart and is pumped to the whole body. There it passes through pores in the flesh into the veins through which it returns from the periphery everywhere to the centre, from the smaller veins into the larger ones, finally coming to the vena cava and right atrium. This occurs in such an amount, with such an outflow through the arteries and such a reflux through the veins, that it cannot be supplied by the food consumed. It is also much more than is needed for nutrition. It must therefore be concluded that the blood in the animal body moves around in a circle continuously and that the action or function of the heart is to accomplish this by pumping. This is only reason for the motion and beat of the heart."*

Summarize events of the cardiac cycle.

The chambers are relaxed (diastole) and both atria collect blood from veins. The sinoatrial node sends impulses initiating contraction of the atria, Blood is pushed into the ventricles by contraction of atria (systole). The atrioventricular valves are open as the atria contract and the semilunar valves are closed so that ventricles fill with blood. \n \n When the ventricles contract (systole), the atrioventricular valves close (preventing backflow) and blood is pushed out through the semilunar valves into pulmonary artery and aorta. When the ventricles relax (diastole) the semilunar valves close preventing backflow of blood.

Outline events of atrial diastole.

At the beginning of the cardiac cycle, both the atria and ventricles are relaxed (diastole). Blood is flowing into the right atrium from the superior and inferior venae cavae. Blood flows into the left atrium from the four pulmonary veins. The left and right atrioventricular valves are both open, so blood flows unimpeded from the atria and into the ventricles. The pulmonary and aortic semilunar valves are closed, preventing backflow of blood into the right and left ventricles from the pulmonary artery on the right and the aorta on the left.

Explain the pressure changes in the left atrium during the cardiac cycle.

Blood flows according to pressure gradients— it moves from regions that are higher in pressure to regions that are lower in pressure. Accordingly, when the heart chambers are relaxed (diastole, A), blood will flow into the atria from the veins and from the atria into the ventricles along the pressure gradient. \n \n When the sinoatrial node triggers the muscles in the atria to contract (atrial systole, B), the pressure within the atrial chambers increases, which forces more blood flow across the open atrioventricular valves, leading to a rapid flow of blood into the ventricles. \n \n The atria relax and the pressure again decreases (atrial diastole, A).

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Explain the relationship between atrial and ventricular pressure and the opening and closing of the atrioventricular valves.

When both diastole: open

Atria systole: open

Ventricle systole: closed

Explain the relationship between structure and function of arteries.

Blood under the highest pressure (closest to pump from heart) \n \n Thickest wall (to withstand high pressure and maintain blood pressure) \n \n Three wall layers (tunica intima, media and externa) \n \n Smooth endothelium (reduces friction as blood moves through) \n \n Smooth muscle (contracts to maintain blood pressure) \n \n Elastic fibers (give wall strength and the ability to recoil to propel blood forward) \n \n No valves (high pressure maintains blood flow direction) \n \n Narrow lumen (maintains high pressure)

Explain the relationship between structure and function of capillaries.

One wall layer (tunica intima) \n \n Wall has one layer of cells (allowing fast diffusion of substances) \n \n Pores and fenestrations (increase permeability for exchange of substances and to allow immune phagocytes to enter tissues) \n \n Extensive branching (increases surface area for exchange of materials) \n \n Narrowest lumen diameter (allows them to fit between cells and perfuse tissue) \n \n Only one red blood cell allowed to pass at a time (for efficient oxygen uptake)

Explain the relationship between structure and function of veins.

Three wall layers (tunica intima, media and externa) \n \n Thin tunica media with less muscle and elastic fibers (allows skeletal muscles to exert pressure on veins) \n \n Widest lumen diameter ( allows great volume of blood to pass while minimizing resistance to blood flow) \n \n Valves (prevent backflow of blood)

Explain how the human body defends itself against pathogens.

1. first time of defense against pathogens by skin and mucous membranes


1. Skin provides a physical barrier and mucus traps pathogens
2. Tears and mucus contain the enzyme lysozyme which destroy bacterial cell walls
3. stomach, skin and vaginal mucus produce acid which kills pathogens
2. If there is a cut in the skin, platelets activate the clotting cascade, creating a clot so pathogens cannot ente
3. If a pathogen makes it through those physical and chemical defenses, then phagocytic white blood cells can ingest and digest pathogens. These phagocytes provide non-specific immunity to disease.Specific immunity is provided by lymphocytes. Lymphocytes divide to produce clones of plasma cells which produce antibodies that are specific to an antigen. The binding of an antibody to an antigen stimulates destruction of the pathogen. Memory cells provide immunity against future attacks by the same antigen.

Explain the role of various proteins in the immune defense against pathogens. 

**Clotting Factors**

Clotting factors are proteins that catalyze the blood clotting process. For example, thrombin is an enzyme that converts fibrinogen to fibrin. Fibrin is a protein that forms a mesh around a platelet plug that forms a clot and prevents the entry of pathogen into the blood.

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**Antibodies**

Immunoglobulins are antibodies. Antibodies are proteins made by plasma B cells that are specific to certain an antigens. Once an antibody binds to an antigen, it inactivates the antigen. 

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**Digestive Enzymes**

Lysozyme is an enzyme that catalyzes the destruction of the cell walls of certain bacteria. There are also enzymes in the lysosome of phagocytic white blood cells digest the pathogens that have been phagocytosed by the cell.

Define “pathogen”

A pathogen is a bacterium, virus, fungus or other microorganism that can cause disease can produce infectious disease.

Outline the role of skin in the defense against pathogens.​

* has a slightly acidic pH which prevents some bacteria from growing.
* secretes antimicrobial fatty acids.
* is relatively dry, which inhibits some bacterial growth.
* is populated with beneficial bacteria that prevent other bacteria from growing.
* secretes sweat, which contains the antimicrobial lysozyme enzyme (catalyzes the destruction of the cell walls of certain bacteria).

Outline the role of sebaceous glands in the defense against pathogens.​

Sebaceous glands in the skin secrete an oil called sebum that is released onto the skin surface through hair follicles. This sebum provides a layer of defense by helping seal off the pore of the hair follicle, preventing bacteria on the skin’s surface from invading sweat glands and surrounding tissue. \n \n Additionally, some bacteria of the microbiome can digest sebum, using it as a food source. This produces oleic acid, which creates a mildly acidic environment on the surface of the skin that is inhospitable to many pathogenic microbes.

Outline the role of mucous membranes in the defense against pathogens.​

A mucous membrane (mucosa) is a tissue that lines cavities in the body at openings such as the eyes, ears, inside the nose, inside the mouth, lip, vagina, the urethral opening and the anus. Mucous membranes secrete mucus, a thick protective fluid. \n \n As a sticky fluid, mucus traps pathogens and prevents them from entering the body. Additionally, mucus can be acidic (eg in the stomach) which will kill some microbes. Mucus also contains the antibacterial enzyme lysozyme, which catalyzes the destruction of the cell walls of certain bacteria.

Outline the role of clotting factors in the blood clotting cascade.

1. cause platelets to become sticky and adhere to the damaged region to form a solid plug.
2. initiate vasoconstriction to reduce blood flow through the damaged region.
3. trigger a series of reactions that ends with the formation of a mesh of fibers around the platelet plug that traps blood cells to form a temporary, insoluble clot.

Outline two roles of platelets in the blood clotting cascade.​

1. When platelets come across the injured endothelium cells, they change shape, aggregate and adhere to each other at the damaged vessel wall. As platelets accumulate at the site, they **form a mesh that plugs the injury**.
2. Platelets release clotting factors in the blood. When a blood vessel is injured, the clotting cascade is initiated and each clotting factor is activated in a specific order to lead to the formation of the blood clot.

Outline the role of thrombin in the blood clotting cascade.

Thrombin is an enzyme involved in the blood clotting cascade. 

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In order to prevent blood from clotting when it shouldn't, thrombin circulates in an inactive form called prothrombin. Prothrombin is produced and secreted into the blood by hepatocytes in the liver.

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Prothrombin is activated by clotting factors, which are released by platelets when a blood vessel is damaged. Clotting factors trigger the conversion of prothrombin to thrombin. Platelets have thrombin receptors on their surfaces that bind thrombin molecules. In turn, **the thrombin enzyme converts soluble fibrinogen into insoluble strands of fibrin**, which form the blood clot.

Summarize the steps of the blood clotting cascade.

The process by which blood clots are formed involves a complex set of reactions collectively called the clotting cascade. This cascade is stimulated by **clotting factors** released from platelets and/or a damaged vessel wall. 

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Clotting factors trigger the conversion of the inactive **prothrombin** into the activated enzyme **thrombin**, which in turn catalyses the conversion of the soluble plasma protein **fibrinogen** into an insoluble fibrous form called **fibrin.** The fibrin strands form a mesh of fibres around the platelet plug and traps blood cells to form a **clot**.

List example disease defenses that provide non-specific immunity.

1. Lysozyme enzyme in tears, digest bacterial cell wall
2. Mucus, which traps bacteria and small particles
3. Skin, a physical barrier
4. Low pH of sweat, prevents growth of bacteria
5. Stomach acid, pH denatures microbial enzymes
6. Fatty acids in sweat, inhibit the growth of bacteria
7. Fever, temperature denatures microbial enzymes
8. Cilia in trachea, keep air passages free from pathogens
9. Phagocytic white blood cells, engulf and digest pathogens
10. Normal microbiome of the skin and in the gut can prevent the colonization of pathogenic bacteria by secreting toxic substances or by competing with pathogenic bacteria for nutrients or attachment to cell surfaces

Compare nonspecific with specific immune responses.

**Nonspecific**

Innate.

Present and ready at all times to respond to a pathogen.

Not antigen specific and reacts equally well to a variety of pathogens.

Does not demonstrate immunological memory.

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**Specific**

Acquired with exposure to pathogens.

Requires some time to amp-up reaction to a pathogen.

Reacts only to a specific antigen specific.

Demonstrates immunological memory. It “remembers” that it has encountered an invading organism and reacts more rapidly on subsequent exposure to the same organism. 

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Describe the function of antibodies.

1. Tag the pathogen or an infected cell for destruction by a phagocyte (opsonization).
2. Block the harmful effects of the toxin (neutralization).
3. Cause clumping for easier capture by phagocytes (agglutination).

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Explain antibody production.

There is a huge variety in the antibodies produced by the B cell lymphocytes. Each antibody recognizes one specific antigen. If the antigen is detected by the immune system, the B cell responds by repeatedly dividing to form many clones. The cloned B cells secrete antibodies against the specific antigen. The binding of an antibody to an antigen stimulates destruction of the pathogen. Some of the cloned B cells will be long lasting memory cells that provided continued immunity if the antigen is again detected.

Define “lymphocytes”

Lymphocytes are a type of white blood cell. There are B and T type lymphocytes. \n \n B lymphocytes produce antibodies. Antibodies attach to a specific antigen and make it easier for the immune cells to destroy the antigen. \n \n T lymphocytes attack antigens directly. They also release chemicals, known as cytokines, which control the entire immune response.

Outline the mechanisms by which antibiotics kill prokaryotic cells.

1. block bacterial cell wall synthesis. Without support from a cell wall, pressure inside the cell becomes too much and the cell bursts.
2. inhibit the 70s bacterial ribosomes and prevent them from building proteins. A bacterium that cannot build proteins cannot survive.
3. cause the DNA strands to break and then prevent the breaks from being repaired. Without intact DNA, bacteria cannot live or reproduce.

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Outline how genes confer antibiotic resistance to bacteria.

Several mechanisms have evolved in bacteria which confer them with antibiotic resistance. Most, but not all, resistance mechanisms are encoded by genes located on plasmids. These genes for code proteins that either: \n \n 1. chemically modify the antibiotic in such a way that it no longer affects the bacteria (most common). \n \n 2. transport the antibiotic out of the cell. \n \n 3. modify the target of the antibiotics action so that it is not recognized by the antibiotic.

List five measures that can be taken to avoid the development of antibiotic resistance in bacteria.

1. Doctors should not prescribe antibiotics inappropriately, such as for the treatment of non-serious infections.
2. Antibiotics should not be prescribed to treat diseases caused by viruses.
3. Patients should always complete the full course of antibiotics to ensure all bacteria are killed and none survive to mutate and form resistant strains.
4. The agricultural use of antibiotics should be restricted.
5. Antibiotics should be disposed of properly, to avoid the chemicals contaminating environmental bacterial populations.

State an example of a multidrug resistant bacteria.

A notorious example of multidrug resistant bacteria is methicillin-resistant *Staphylococcus aureus* (MRSA), which is resistant to most antibiotics and disinfectants. MRSA can act as a major source of hospital-acquired infections and cannot be treated easily.

Define coronary thrombosis.

Coronary thrombosis is the formation of a blood clot inside a blood vessel of the heart. This blood clot restricts blood flow within the heart and can lead to myocardial infarction (heart attack).

Outline the relationship between HIV and AIDS.

HIV attacks cells of the immune system. Without treatment, the virus will reduce the number of functional T cells. In the advanced stages of HIV infection, loss of the T cells leads to the symptomatic stage of infection known as the acquired immunodeficiency syndrome (AIDS). Symptoms of AIDS include:

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Rapid weight loss

Recurring fever or night sweats

Extreme and unexplained tiredness

Prolonged swelling of the lymph glands 

Diarrhea

Sores of the mouth, anus, or genitals

Pneumonia

Describe two functions of the fluid secreted by Type II pneumocytes.

1. Reinflation of the alveoli following exhalation is made easier by the surfactant, which reduces surface tension in the thin fluid coating of the alveoli.
2. facilitates the transfer of gases between blood and alveolar air. The gases dissolve in the moist fluid, helping them to pass across the alveoli surface.

List symptoms of lung cancer.​

Lung cancer typically doesn't cause signs and symptoms in its early stages. Signs and symptoms of lung cancer typically occur only when the disease has advanced. \n \n Signs and symptoms of lung cancer may include:

* A persistent cough
* Coughing up blood
* Shortness of breath
* Chest pain
* Voice hoarseness
* Unintentional weight loss

State the symptoms of emphysema.

Shortness of breath and cough are the main symptoms of emphysema. As the disease progresses, other symptoms include: \n

* Fatigue
* Weezing
* Chest tightness
* Anxiety

List treatment options for people with emphysema.

The damage from emphysema is permanent. The ability to breathe properly cannot be fully recovered. Treatment of emphysema aims to ease symptoms and stabilize the condition. \n \n Treatments include:

* supplemental oxygen
* inhaled bronchodilators
* inhaled steroids
* smoking cessation
* lung surgery to remove damaged tissue
* lung transplant

Outline techniques for measuring lung tidal volume.

1. A spirometer is a device that measuring the volume of air inspired and expired by the lungs. It operates by measuring the velocity and/or pressure of the airflow as it moves past a sensor.
2. Air can be exhaled into a lung volume bag. The bag will trap the exhaled air inside and the volume on the bag’s scale can be measured.
3. Air can be exhaled through a tube that ends in a inverted flask of water. The exhaled air will displace a measurable volume of water.

Outline techniques for measuring ventilation rate.

1. A spirometer is a device that measuring the rate of air inspired and expired by the lungs. It operates by measuring the velocity and/or pressure of the airflow as it moves past a sensor.
2. Simple observation and counting number of breaths per minute.

Outline how the nervous system responds to information about the internal and external environments.

The nervous system produces a response based on the chemical and/or physical stimuli perceived. The nervous system can activate contraction of all three types of muscle tissue (skeletal, smooth and cardiac). The nervous system can also stimulate glands (exocrine and endocrine).

State the relationship between neuron axon diameter and speed of electrical impulse.

Larger diameter axons conduct neural impulse faster than smaller diameter axons because the local current diffusion of Na+ spreads faster down a wide axon than down a narrow one. A larger diameter axon offers less resistance to the movement of ions down the axon, causing the impulse to be conducted faster.

State the function of the neuron motor end plate.

Motor end plates are located at the end of a motor neuron axon, opposite the cell body. Motor end plates are the presynaptic terminal where a motor neuron connects to a target muscle cell. It is from the motor end plant that a motor neuron is able to transmit a chemical signal to the muscle cell, causing muscle contraction.

State the role of Schwann cells in formation of myelin.

Myelin around motor neuron axons is produced by Schwann cells. Schwann cells hold the neurons in place, supply them with nutrients and provide insulation.

Define “saltatory conduction”

Saltatory conduction is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node. The action potential “jumps” from one node to the next.

Outline three mechanisms that together create the resting potential in a neuron.

**Sodium-potassium pump**

A membrane bound protein pump that actively transports three sodium (Na+) out of the cell for every two potassium (K+) into the cell. As more cations are expelled from the cell than taken in, there is a net loss of 1 positive charge with each action of the sodium-potassium pump. As a result, inside of the cell becomes negatively charged relative to the outside of the cell.

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**Anions within the cell**

Anions are ions with negative charge. The inside of the neuron contains anions such as Cl- ions, negatively charged proteins, inorganic phosphate groups and DNA. 

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**"Leaky" K+ channels**

K+ can move passively through channel towards the outside the cell, taking it's positive charge with it and leaving the inside of the cell relatively more negative.

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Summarize the action of the sodium-potassium pump.

1. Three Na+ ions bind to the pump from the inside of the cell.
2. ATP binds to the pump. 
3. ATP is hydrolyzed, leading to phosphorylation of the pump and release of ADP. As a result of phosphorylation, the pump undergoes a conformational change. The phosphorylated form of the pump has a low affinity for Na+ ions, so they are released to the outside of the cell. 
4. Two K+ ions bind to the pump from the outside of the cell. 
5. Binding of the K+ ions causes the dephosphorylation of the pump, reverting it to its original conformation.
6. The two bound K+ ions are released to the inside of the cell. 

Define “action potential”

An action potential is the temporary change in electrical potential with the passage of an impulse along the membrane of a muscle cell or nerve cell. In other words, an action potential is the "flip-flop" in charge (from negative, to positive and back to negative) that occurs in the neuron or muscle cell membrane.

Summarize the action of a voltage-gated ion channel.

A voltage-gated ion channel is an ion channel that opens and closes in response to changes in the membrane potential of a cell.

Outline the mechanism of neuron depolarization.

A stimulus triggers the opening of Na+ channels in the membrane. The stimulus may be a neurotransmitter binding to its receptor protein or physical stimulus of a sensory neuron.

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Because the concentration of Na+ is higher outside the cell than inside the cell, Na+ ions will rush into the cell when Na+ channels open. Sodium is a positively charged ion, so the sodium cation entering the cell will cause the local charge near the channel to become positive. As the charge rises and the threshold voltage is reached, additional voltage-gated Na+ channels open and even more Na+ ions will enter the cell. The membrane potential will reach +40 mV. This is known as **depolarization**.

**Describe how nerve impulses are propagated along the neuron axon.**

Some of the Na+ that moves into the cell during depolarization diffuses within the cell, increasing the charge of adjacent regions of the cell. This is called the local current. The increase of charge with the local current affects adjacent channels, causing action potential depolarization in the next region of the cell membrane. This sequence of adjacent action potentials is the "impulse" that propagates along the neuron.

Define “local current”

Local current is the diffusion of Na+ ions within the cell following depolarization. Local current results in the subsequent depolarization of the adjacent membrane and if this area reaches threshold potential, further action potentials are generated.

Explain movement of sodium ions in a local current.

Going down the length of the neuron axon, the action potential is propagated because more voltage-gated Na+ channels are opened as the depolarization spreads. This spreading occurs because Na+ enters through the channel and diffuses along the inside of the cell membrane. As the Na+ moves, its positive charge depolarizes a little more of the cell membrane. As that depolarization spreads, new voltage-gated Na+ channels open and more ions rush into the cell, spreading the depolarization a little farther.

Explain why some synaptic transmissions will not lead to an action potential in a postsynaptic cell.

Neurotransmitters can increase (excitatory) or decrease (inhibitory) the probability that the cell with which it comes in contact will produce an action potential. \n \n Inhibitory neurotransmitters cause hyperpolarization of the postsynaptic cell (which means, decreasing the voltage gradient of the cell, thus bringing it further away from an action potential).

Outline the functions of the acetylcholine neurotransmitter.

Acetylcholine (ACh) is the neurotransmitter used at the neuromuscular junction; it is the chemical that motor neurons release in order to activate muscles. \n \n Acetylcholine also plays important roles in cognitive function, most notably in the neural mechanisms of memory, alertness, attention, and learning.

State the reason why neurotransmitter molecules must be inactivated after secretion. 

to prevent constant stimulation of the postsynaptic cell and an excessive firing of action potentials (or inhibition of action potentials for inhibitory neurotransmitters)

Outline the mechanism of reabsorption of the neurotransmitter acetylcholine.

Following dissociation from the receptor, acetylcholine is rapidly hydrolyzed by the enzyme acetylcholinesterase. The enzyme converts acetylcholine into its inactive component parts choline and acetate. \n \n After hydrolysis, acetate quickly diffuses into the surrounding medium, while choline gets taken back into the presynaptic cell. Choline is then recycled by the presynaptic cell for use in the synthesis of more acetylcholine.

Outline the use of oscilloscopes in measuring membrane potential.

An oscilloscope is a instrument that graphically displays varying signal voltages over time. A microelectrode is inserted into the cell and a reference electrode is placed outside the cell. The oscilloscope measures the difference in voltage between the inside and outside of the cell.

Define “hormone”

A hormone is a molecule released by a cell in a multicellular organism that influences the behavior of another cell within the same organism. Hormones are secreted from one cell and bind to a specific receptor on (or in) the target cell. Hormones are used to coordinate and control everything from metabolism to behavior.

Describe the function of thyroxine.

Thyroxine is a hormone secreted into the bloodstream by the thyroid gland. All cells in the body are likely targets for thyroid hormones. Thyroid hormones play vital roles in regulating the body’s metabolic rate and are essential for normal development, growth, and neural differentiation.

List symptoms of thyroxine deficiency.

Too little production of thyroxine by the thyroid gland is known as **hypothyroidism**. It may be caused by autoimmune diseases, low iodine intake or by the use of certain drugs. 

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Thyroid hormones are essential for physical and mental development so untreated hypothyroidism before birth or during childhood can cause mental impairment and reduced growth. 

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Hypothyroidism in adults causes reduced metabolism. It can result in symptoms such as fatigue, decreased body temperature, weight gain, poor memory, depression, stiffness of the muscles and reduced fertility. 

List symptoms of thyroxine over production.

Overproduction of thyroxine by the thyroid gland is known as **hyperthyroidism**. It may be caused by overactivity of the thyroid gland, autoimmune diseases, inflammation of the thyroid or a benign tumour. Hyperthyroidism is often recognised by a goitre, which is a swelling of the neck due to enlargement of the thyroid gland.

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Common symptoms of hyperthyroidism include increased body temperature, nervousness, insomnia, high heart rate, eye disease and anxiety.

Outline the function of endocrine glands.

Endocrine glands are glands of the endocrine system that secrete hormones directly into the blood. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid, parathyroid, hypothalamus and adrenal.

Outline how thyroxine regulates metabolic rate and body temperature based on negative feedback mechanisms.

Neurons in the brain (hypothalamus) sense circulating levels of thyroid hormone. \n \n If blood concentrations of thyroid hormones increase above a certain threshold, the thyroid stops thyroxine secretion until the levels in the blood return to normal. \n \n If thyroid hormone levels drop below the threshold, the thyroid is stimulated to produce and secrete thyroxine until levels in the blood return to normal.

Outline the mechanism of action of leptin.

Leptin is a hormone secreted into the bloodstream by adipose cells. If the amount of adipose tissue increases, blood leptin concentration rises. Leptin acts on cell receptors in the hypothalamus. Leptin helps to regulate energy balance by causing the **hypothalamus** to inhibit appetite, which in turn diminishes fat storage in adipocytes.

Describe the action of melatonin.

Melatonin is a hormone secreted into the bloodstream by the **pineal gland**. Melatonin regulates the sleep-wake circadian rhythm in mammals. Melatonin is a protein hormone that binds to melatonin receptor proteins embedded in target cell membranes. Melatonin receptors are found throughout the body in places such as brain, retina, cardiovascular system, liver and gallbladder, colon, skin, and kidney.

Describe the mechanism by which the SRY gene regulates prenatal gonad development.​​ ​

The sex-determining region Y (*SRY)* gene is found on the Y chromosome. The *SRY* gene provides instructions for making a protein called the sex-determining region Y protein (also called testis-determining factor, TDF). The protein acts as a transcription factor, which means it attaches to specific regions of DNA and helps control the activity of particular genes. The protein initiates processes that cause a fetus to develop male gonads (testes) and suppresses genes that are important in development of female reproductive structures. 

Outline role of testosterone in prenatal development of male genitalia.

Male phenotypic differentiation of the bipotential gonad depends on the presence of the SRY gene on the Y chromosome. The gene codes for a protein called the sex-determining region Y protein (also called testis-determining factor, TDF). The protein acts as a transcription factor and initiates processes that cause the bipotential gonad to develop into testes. \n \n The fetal testes then begin to produce testosterone. Testosterone stimulates the development of the male reproductive structures during fetal development; the penis, the epididymis, the seminal vesicles, the prostate and the duct systems.

State testosterone's role in stimulating the primary sexual characteristic of males.

Soon after the formation of the testis, the Leydig cells within the testes begin to secrete testosterone. Testosterone can influence tissues to become the male primary sexual characteristics during fetal development. \n \n Male primary sexual characteristics are the external and internal reproductive structures present at birth: the penis, the epididymis, the seminal vesicles, the prostate and the duct systems.

State the sources of estrogen and progesterone used in prenatal development.

In placental mammals, both female and male fetuses are bathed in estrogens and progesterone of maternal origin (hormones from the mom and the placenta). Development of female reproductive structures is independent of maternal estrogen and progesterone (rather, female sex determination is based on absence of SRY gene). Once developed, the fetal ovary does not contribute significantly to circulating estrogens. The female fetus ovary has no documented role in differentiation of the female genital tract.

Outline events occurring during the follicular phase of the menstrual cycle.

The follicular phase starts on the first day of menstruation and ends with ovulation (typically day 14).

Prompted by the hypothalamus, the pituitary gland releases follicle stimulating hormone (FSH). This hormone stimulates the ovary to produce 5 to 20 follicles (tiny nodules or cysts), which bead on the surface of the ovary. Each follicle contains an immature egg and secretes estrogen. \n \n As the follicular phase progresses, one follicle in one ovary becomes dominant and continues to mature. This dominant follicle suppresses all of the other follicles in the group. As a result, they stop growing and die (around day 10). The dominant follicle continues to produce estrogen. Estrogen stimulates the lining of the uterus (endometrium) to thicken in preparation for possible pregnancy.

Outline events occurring during the luteal phase of the menstrual cycle.

The luteal phase begins at ovulation and ends with the start of menstruation (days 14-28). \n \n After ovulation, the pituitary hormones FSH and LH released from the anterior pituitary cause the remaining parts of the dominant follicle to transform into a structure known as the corpus luteum. This structure starts releasing progesterone, along with small amounts of estrogen. This combination of hormones maintains the thickened endometrium lining of the uterus, waiting for a blastocyst to implant. \n \n If a blastocyst implants in the lining of the uterus, it produces the hormones that are necessary to maintain the corpus luteum. The corpus luteum keeps producing the raised levels of progesterone that are needed to maintain the thickened lining of the uterus during the pregnancy. \n \n If implantation of a does not occur, the corpus luteum withers and dies, usually around day 22. The resulting drop in progesterone level causes the endometrium lining of the uterus to fall away (menstruation).

State the source and location of action of LH (luteinising hormone) in the menstrual cycle. 

Luteinising hormone (LH) is a protein hormone produced and released by cells in the anterior pituitary gland. In females, LH moves through the blood and binds to receptor proteins found on ovary cells.

State the source and location of action of FSH (follicle stimulating hormone) in the menstrual cycle.

Follicle stimulating hormone (FSH) is a protein hormone produced and released by cells in the anterior pituitary gland. In females, FSH moves through the blood and binds to receptor proteins found on ovary cells, where it stimulates the growth of follicles (and resulting increased estrogen production) during the follicular phase of the menstrual cycle.

State the source and location of action of estrogen in the menstrual cycle.

Estrogens are steroid hormones produced by the ovaries (follicle and corpus luteum). In the menstrual cycle, the target tissue for estrogen action is the uterus, where it causes growth of the endometrial lining. Estrogen penetrates the cell surface and binds to an estrogen receptor protein in the cytoplasm of the cells. The estrogen-receptor complexes enter the cell nucleus, where it binds to DNA and influences the rate at which particular genes are transcribed.

State the source and location of action of progesterone in the menstrual cycle. 

Progesterone is a steroid hormone produced by the corpus luteum of the ovary during the luteal phase of the menstrual cycle. In the menstrual cycle, the target tissue for progesterone action is the uterus, where it prepares the endometrium for pregnancy in the event that the released egg is fertilized. \n \n Progesterone penetrates the cell surface and binds to a progesterone receptor protein in the cytoplasm of the cells. The progesterone-receptor complexes enter the cell nucleus, where it binds to DNA and influences the rate at which particular genes are transcribed.